Underground pressure vessel construction method

ABSTRACT

997,538. Wells, &amp;c. FENIX &amp; SCISSON Inc. July 14, 1961 [July 15, 1960], No. 25702/61. Heading E1F. [Also in Division F4] In excavating a subterranean cavern for the storage of liquid petroleum gas (see Division F4) a shaft 38 Fig. 1 is sunk to below the roof level 43 of the proposed cavern, the extension is filled with sand 44 and a steel liner 39 in welded sections is lowered into the shaft, said liner having utility conduits 45, Fig. 2, welded to the exterior thereof thus leaving the interior of the liner free of obstruction thereby facilitating the removal of the sand 44 and of subsequently excavated earth and rock. Each liner section has external handling and locating lugs 53, 54, Fig. 6, welded thereto and the lower end of the first liner section is closed by a cast concrete slab 41 supported by rods 42 which allows water poured into the liner to serve as ballast to assist lowering of the first liner section and of sections subsequently welded thereto. The space between the shaft wall and the liner is filled with cement grouting 40, water is pumped out, slab 41 drilled out, sand 44 removed and the cavern excavated by conventional means. Finally the bottoms of conduits 45 are closed, sections 46, Fig. 4, are cut out of the liner at a predetermined level, conduits 45 cut, grouting 40 removed to provide a space 47 sections 46 replaced and cement is forced down one conduit 45 into space 47 thus effecting a permanent seal and the upper end of the liner is closed by a cap 71, Fig. 7 (not shown).

Nov. 9, 1965 3,216,200

UNDERGROUND PRESSURE VESSEL CONSTRUCTION METHOD 5. E. sclssoN ETAL 4Sheets-Sheet 1 Filed July 15, 1960 INVENTOR GILBERT J. FE/V/X syn/v5) E.SG/SSON /59A WM,

ATTORNE 8 1965 s. E. SCISSON ETAL 3,216,200

UNDERGROUND PRESSURE VESSEL CONSTRUCTION METHOD 4 Sheets-Sheet 2 FiledJuly 15, 1960 INVENTOR GILBERT J. FE/VIX SYDNEY E. SUISSON ATTORNEYSUNDERGROUND PRESSURE VESSEL CONSTRUCTION METHOD Filed July 15, 1960 1965s. E. SCISSON ETAL 4 Sheets-Sheet 3 IN VENTOR ATTORNEYS GILBERT J. FEN/X SYDNEY E. SG/SSON /ZZH m VM 6 s. E. SCISSON ETAL 3,216,200

UNDERGROUND PRESSURE VESSEL CONSTRUCTION METHOD Filed July 15, 1960 4Sheets-Sheet 4 IN VENTOR a GILBERT J PEN/X SYDNEY E. SCISSON r QAMYMQATTORNEYS United States Patent O 3,216,200 UNDERGROUND FRESSURE VESSELCONSTRUCTION METHOD Sidney E. Scissor], 5805 E. th St, Tulsa, Okla, and

Gilbert J. Fenix, Phoenix, Ariz. (5805 E. 15th St.,

Tulsa, Okla.)

Filed July 15, 1960, Ser. No. 431% 2 Claims. (Cl. 6l40) The presentinvention relates to underground storage systems and more particularlyto an improved underground pressure vessel storage system and methods oflocation, design, and construction thereof.

Because of the numerous disadvantages inherent in the surface storage ofgases and liquid, underground caverns have long been utilized to storesubstances such as hydrocarbon liquids and gases. For instance, storageof fluids has been effected in washed out salt cavities and in someinstances, mined or dug caverns have also been constructed specificallyfor the storage of fluids.

Obviously the sparsity of salt deposits for fluid storage seriouslylimits the storage capacity available from these sources. Also, mined ordug caverns, as they were known prior to this invention, have notcompletely fulfilled the pressing need for storage space underground.The mining of a storage cavern is an inherently hazardous, costly anddiflicult operation. Only certain earth formations and strata can beused for storage and some of them only for certain fluids. Thedifliculties of digging the cavern, including those of the furnishing oflighting, power, air and machinery to the miners, removal of minedmaterial, leakage of polluting foreign substances from fissures into thecavern and migration or escape of the stored fluid or gases, and manyother difiiculties, all combine to render previously known methods ofcavern construction unsatisfactory. Frequently, for example,considerable work is accomplished toward building the storage cavernbefore it is discovered that the location must be disregarded due tounsatisfactory characteristics of the encountered strata because ofporosity, permeability, compressive strength or reaction to the productwhich is to be stored. Moreover, all too frequently, serious rockfractures, which render a location unfit for storage are not discovereduntil much later after important expenses have already been incurred.Further, errors have been made due to improper determinations in theexisting hydrostatic (ground-water) head in the area surrounding theunderground storage vessel. This results in the completed vessel nothaving the capability of maintaining the stored product under desired ornecessary pressures.

Briefly stated, the general purpose of this invention is to provide animproved underground pressure-vessel storage system, and methods oflocation and construction thereof, which lessen or eliminate the abovedescribed disadvantages. To attain this, the present invention conplatesa unique method of location and pretesting of a proposed storage cavernsite by simulating actual operational conditions on strata test Zonesprior to extensive mining operations. In addition, the inventionprovides a unique method for initiating and conducting the miningoperation through an improved entrance having superior provisions forthe furnishing of auxiliary power, light, etc., to the miners andincorporates an improved sealing arrangement for this entrance. Theentrance casing as installed in the manner disclosed provides a barrierto surface and ground water, quicksand, etc. from gaining access to theentrance proper. In other words as each liner section is lowered intothe shaft, it acts as a barrier to surface cave-ins, ground-water,seepage and the like. It is therefore an object of this invention toprovide an access to the storage vessel of this invention comprising"ice basically only the bored or drilled shaft and a liner insert. As aresult, it is not necessary to use explosives during the construction ofthe access means. This is of great importance in areas where aboveground storage facilities already exist.

Furthermore, by the practice of the instant invention structurally weakor fractured formations, heretofore usually considered unusable forpressure storage vessels, are rendered completely satisfactory for fluidor gaseous storage application.

Another object is to provide an improved pressure vessel system whichmay be installed in locations formerly considered unsuitable forunderground storage.

A further object of the instant invention is to provide a unique methodof excavating and otherwise constructing underground caverns for thestorage of liquids, gases, solids, and/or mixtures thereof such asatomic or atomic waste materials.

Yet another object of the present invention is the provision of animproved storage system for underground storage having a greatstructural integrity and characterized by flexibility of operation andwhich is capable of construction in a relatively inexpensive andexpeditious manner.

A still further important objective of this invention is to provide amethod of constructing an underground storage vessel which affordsmaximum safety to personnel during the mining operation.

Still further, the present invention provides as an objective, anunderground vessel which is substantially safer to the surroundingcommunities in the event of an explosion, and the likelihood ofexplosion is reduced due to the impossibility of personnel gainingaccess to the completed vessel.

Other objects and advantages of the invention will hereinafter becomemore fully apparent from the following description of the annexeddrawings, which illustrate a preferred embodiment, and wherein:

FIG. 1 is a schematic showing of a hydraulic test apparatus suitable forpretesting rock strata for hydraulic pressure vessel characteristics;

FIG. 2 illustrates schematically, apparatus suitable for pretesting gasor hydraulic pressure characteristics of earth or rock strata;

FIG. 3 is a vertical section of the cavern entrance illustrating onemanner of placing the entrance tube or liner;

FIG. 4 shows a plan view of the cavern entrance tube and padinstallation of the utility conduits;

FIG. 5 is a vertical section of the entrance tube at the earths surfaceillustrating the manner of surface sealing the utility conduits;

FIG. 6 is a detail view in vertical section showing the manner ofsealing utility conduits and entrance tube below the earths surfaceafter completion of the excavations;

FIG. 7 is a vertical partial section at the lower terminus of theentrance tube showing the capped utility conduits and a method ofreinforcing the cavern roof or ceiling;

FIG. 8 is a fragmentary showing of a typical entrance tube and themanner of afiixing the spacing members or centralizers;

FIG. 9 schematically illustrates one typical application of theinvention to an underground storage system for liquified petroleum gasand illustrates a preferred arrangement of pumping, gauging and liquidlevel indicating equipment; and

FIG. 10 is a section at one pumping station schematically illustratingthe means provided for removing the pumps from the storage vessels afterthe vessels have been placed in operation.

The caverns or vessels of this invention are of the type capable ofstoring large quantities. The construction and mining of such vesselsare huge undertakings and represent an investment of great magnitude.

Referring now to the drawings, wherein like reference numerals designatelike or corresponding parts throughout the several views, there is shownin FIG. 1 the hydraulic test apparatus of the invention together with aconventional core hole which may be drilled in several locations frompoints overlying the area to be occupied by the pressure vessel. Thecore samples taken are preferably examined and laboratory tested forporosity, permeability, compressive strength, reaction to product to bestored, etc., contemporaneously with the pretesting methods describedhereinbelow.

Assuming a hydraulic test of zone 26 of the strata exposed by core hole10 is desired, inflatable sealing members or packers 12 are lowered intothe core hole by means of a cable 13 to the desired depth. Connected tothe packers 12 through high pressure hose 14, gauge 19, stop valve 25and the upper portion of line is a tank of liquid 22. To inflate thepackers and thus seal off the area designate-d 26 for hydraulic test,venting valve 18 is opened to permit the escape of entrapped air, valveis opened and valve 24 is closed. Actuation of a wobble pump 21 willfill line 14 with liquid. Vent 18 is closed and continued pumping willinflate packers 12to desired sealing pressure. Gauge 19 records thesealing pressure in line 14 which is conveniently carried to about 75psi. above the test pressure contemplated for area or zone 26. Valve 25is then closed to isolate the packer sealing pressure.

The pipe 11, which holds packers 12 in proper spaced relationship isconnected to and is in communication with the interior of hose 15 whichis provided with a T fitting '16, the exposed leg of which is closed bya rupturable disc. The provision of the disc, it will be appreciated,provides a convenient seal to keep the line free of dirt and alsoensures a leakage test for fittings, hoses and pipes up to the designedrupture pressure of the disc.

To pressurize the core hole in test zone 26, vent 18' in line 15 iscracked or opened and water or other test liquid is pumped by pump 21through opened valve 24 to fill the line 15. Closure of vent 18 permitspressure build-up by pump 21 in line 15 and pipe 11 against the disc inT connection 16. By building up a desired pressure and discontinuing thepumping, gauge 20 may be observed for pressure loss indicating fittingor hose leakage. Continued pumping will rupture the disc in T connection16 and the zone 26 will be subjected to hydraulic pressure test of anydesired amount. By closing valve 24, the pressure in area 26(represented on gauge 20) may be observed for drop-off indicatingleakage in the formation. Any leakage can readily be quantitized withthe described apparatus merely by opening valve 24, pumping additionalliquid to hold the desired pressure and recording the liquid drop. Thismay conveniently be done with such apparatus as sight glasses 23.

To deflate and remove the packers on completion of the test it isusually only necessary to crack vent 18. However, under some conditions,as, for instance, when static water level is low or near the packers 12,the packers may not deflate when valve 18 is opened. To facilitateremoval of the packers in this situation another repturable disc 17 islocated in the extreme terminus of line 14. This disc, it should beunderstood, is considerably stronger than the disc located in Tconnection 16. However, closure of valve 18 and continued pumping willcause it to rupture, deflating the packers and spilling liquid into thecore hole 10. The apparatus may then be readily removed from the corehole.

FIG. 2 illustrates a test apparatus suitable for gas and/ or hydraulicpretesting. The test area is again designated 26 for clarity though itshould be understood that many areas in the same-or in different coreholes may be tested by either hydraulic or gas methods or both. Thisdetermination being one dictated by the geological conditionsencountered and the requirements of the storage system to beconstructed.

Packers 12 may be lowered as described hereinbefore and inflated byopening valve 25 to connected pressurized gas source 21 with highpressure line 14. Valves 24 and 18 should, of course, be closed forproper pressure buildup in the packers. When a suitable sealing pressureis registered on gauge 19, valves 25 and 18 are closed and valves 24 and29 opened. Valves 28 and 27 are normally closed except as describedhereinafter. Gas pressure from source 21 then builds up in line 15against the disc in T connection 16 in pipe 11, as describedhereinbefore, and the test is performed in a similar fashion to thehydraulic test described in connection with FIG. 1, the test pressureexerted on area 26 being computable from the gauge pressure shown ongauge 20.

If it is desired to measure the amount of loss in gallons at area 26, ifsuch exists, the liquid tank 22 may be used. Valve 29 is closed andvalves 27 and 28 are opened. Any loss can then be measured at sightglasses 23 While desired pressure readings are maintained at gauges 19and 20. Upon completing tests, pressure may be released by closing thegas source stop valve and opening valves 18 and 18 in that order.

Having arrived at a suitable location for the pressure vessel on thebasis of design considerations and the test results discussedhereinabove, an entrance to the proposed cavern is begun by drilling ashaft or hole 38, as illustrated in FIG. 3. The shaft length will bedetermined by considerations understood by those skilled in the art, butaccording to the invention, the drilled shaft extends through the roof43 of the cavern to be excavated to a point Well into the vessel, andthe shaft extension is filled with sand 44. A steel liner or tube 39,having a diameter of sufiicient size to permit extraction of minedmaterial from the vessel, and facilitating ingress and egress ofpersonnel and machinery, is next installed. The liner must also be ofsufficient strength to withstand grouting and hydrostatic pressure onthe outside thereof and gas pressure on its interior. It should be notedhere that the tremendous amount of material which must be excavated willbe removed through this single shaft.

Assuming, for illustrative purposes, that the drilling rig is not strongenough to hold the liner 39, provision is herein made to enable theliner to be floated into place. In this instance, the first linersection may be provided with brass rods 42 welded to the lower openingof the bottom line to facilitate supporting a concrete floating plug 41which is poured into the liner section. The brass rods are easilysevered when it is desired to remove the plug.

As shown in FIGS 47 a plurality of utility conduits or lines 45 aresuitably fastened to the exterior surface of the liner 39, as bywelding, and are capped, at the first liner section as clearly shown inFIG. 7.

In order to leave the interior of the liner 39 free from allobstructions the liner sections are preferably beveled at their abuttingsurfaces on the exterior liner circumference and are welded together onthe outside. This feature becomes exceedingly important during theactual mining operation. Huge material removal buckets travel at greatspeeds through the liner. In addition, successive lengths of utilityconduits 45 are added and fastened, as by Welding, on the outside of theliner sections as the whole liner 39, is assembled and lowered into theshaft 38.

To facilitate the welding, handling lugs (not shown) are preferablyaffixed to each liner section so it may be supported above ground forwelding. As each section of the liner or tube 39 is welded to thepreceding section, radially extending centralizers or spacers 53 and 54are attached in circumferentially spaced relation around the liner.These spacers are for the purpose of holding the liner or tube 39 in anupright and spaced relation in the drilled shaft or hole 38 so that apredetermined space is available for grouting the tube 39 into the shaft38.

As will be evident from a perusal of FIG. 8, the spacers designated 54may be substantially more arcuate and thus extend further from the lever39 than the spacers 53. The more arcuate spacers 54 are placed on thesame side of the liner as the utility conduits, such arrangement beingconsidered preferable to ensure that the grout used to hold and seal theliner will completely enclose the entire liner and the utility conduits,and to protect the utility conduits while being lowered into the shaft.

When a concrete plug 41 has been poured in the tube bottom, in instancesin which the liner is to be placed by floating, water is added to theinside of the liner causing it to sink as each line section with itsutility conduits, and centralizers are added. After the liner iscompletely assembled and is resting on sand 44, the space between theliner 39 and the drilled shaft 38 is grouted with a Portland cementgrout 40 or other suitable grouting materials to permanently fasten andseal the liner 39 in the shaft 38. At this time, the entrance slab 48may conveniently be poured, leaving an annular section 49 through whichconduits 45 pass at the surface free of concrete. The annular section 49may be filled with sand.

After the grout 40 has hardened, the water used to sink the linersections is removed and the .plug 41 and rods 42 are drilled out. Sand44 and any water remaining in the shaft extension vacated by the removalof sand 44 may be removed by conventional drilling equipment.

Mining or excavating the cavern proper, according to the invention, isbegun at the top of the intended pressure vessel. By so beginning, thematerial dislodged by blasting or other means will fall naturally intothe void created by the removal of sand 44 leaving room for the minersto work and load excavated material for removal through liner 39. Inthis manner one of the perennial problems of underground excavation issimply and effectively overcome. By removing the caps from the utilityconduits 45, electrical lines, air, water, telephone lines and the likecan be readily made available in the cavern while the liner 39 has itsinterior completely unobstructed and smooth to facilitate the removal ofexcavated rocks and earth and for the free ingress and egress of men andequipment to the cavern being mined.

The particular manner of digging the pressure vessel other than asherein specified is dependent upon considerations too numerous to beconsidered here. Suflice it to say that any conventional method may beemployed the room and pillar method for instance, being one well suitedfor most requirements.

Upon completing the excavation of the vessel the entrance liner ispermanently sealed. Utility lines 45 are again capped at the cavern roof43 and sections 46 of the liner are cut out as shown in FIG. 6. Thedepth below the surface at which sections 46 of the liner are removedmay vary according to the application of the invention. For instance thesection cuts are made at the strongest and most impermeable stratasdetermined by the original pretesting steps.

Referring again to FIG. 6, at the removed section 46, the utilityconduits 45 are cut out, the grout 40 is removed, and material isremoved to solid surface for a grout seal 47. Sections of the liner 39are welded back into position and grout is pumped into the space 47through one utility conduit with the others open at the top. Pumping iscontinued until the grout comes out through the other utility conduitsthus forming a seal under pressure of the column of grout from thesurface to the liner area illustrated in FIG. 6. Additional pressure isapplied at the surface if deemed necessary.

The sand filling in annular space 49 is removed, the utility conduitsare trimmed, if required, and the annular space 49 filled with concretecompleting the upper seal 6 for the liner 39. As may be seen from FIG.9, the liner 39 then has a cap 79 welded or otherwise suitably fastenedon to permanently seal this section of the pressure vessel.

In the underground mining of pressure vessels, structurally weak rockformations are sometimes encountered, that in their natural or fracturedcondition are unsuitable for fluid or gas storage. Should this conditionbe encountered, the surfaces may be reinforced as shown in FIG. 7, bythe use of expansion bolts 50, plates 51 and/or the use of mesh 52. Theplacement of these reinforcing members, of course, are made along sidesurfaces as well as those of the roof as shown. Proper control of thesizes and shape of the vessel and the use of reinforcing means such asthose illustrated frequently make possible the utilization of otherwiseobjectionable earth formations for storage purposes. The expansion bolts50 may be from 4 to 10 feet in length and are inserted in bores whichextend beyond the fracture to solid rock.

It has also been found in practicing the invention that fracturedformations that are not competent in their natural state can be sealedto hold products by pressure grouting. A preferred method ofaccomplishing this desirable result involves drilling a hole or holesfrom within the cavern to intersect the offending fracture at apredetermined distance from the cavern surface. The distance to thepoint of intersection from the cavern surface may vary depending uponthe severity of the fracture. Packers or sealing members are inserted inthe drilled hole and grout is introduced under pressure to seal thefracture. It will be understood that the extent of the pressure groutingof a fractured area usually deemed necessary to hold water inflow, forinstance, to acceptable quantities, will vary depending on such factorsas the hydrostatic pressure of the ground water, the design pressure ofthe vessel and the product to be stored. It should be remembered thatduring the mining and grouting phase of construction, there is nointerior Pressure from the stored gas counteracting the hydrostatichead. After the stored fluid is placed in the container, a balance isstruck between the head and interior pressure which will, in fact, aidin preventing leakage from the vessel.

The final design of the pressure vessel system, as will be understoodfrom the description thus far, may take a variety of forms and performmany storage functions. In FIG. 9 there is schematically illustrated onetypical application of the invention adapted for the underground storageof liquefied petroleum (LP) gas. It should be clearly understood thatthe particular arrangement illustrated, including the shape of thepressure vessel, the location and number of shafts, pumps, etc. isintended as illustrative and should not be interpreted as limitative inany respect. The cavern 60 is illustrated as having a gen erallyrectangular shape with horizontal roof 43 and substantially horizontalfloor 61.

Four auxiliary shafts, 63, 64, 65 and 66 provide communication betweenthe surface '76 and the pressure vessel 60 and house a liquid floatlevel 73 and three conventi-onal LP gas pumping units 74, 75, and 76,respective-ly. The main liner 39 is provided with a gauging unit 79which may include three indicator tubes 80, 81 and 82 accuratelypositioned at predetermined and different heights from the cavern floorand which may be connected to a suitable manometer. As will be apparent,the state of the LP storage is at all times evident to an observer atthe surface through the combined readings available from the liquidfloat indicator 73 and the gauging unit associated with the liner 39.

Upon completion of mining operations, pumping Sumps 85, 86 and 87 ofsuitable depths are drilled in the bottom of the vessel positioned so asto receive casings 64, 65, and 66, respectively. The casings extend to apoint near, but spaced from, the bottom of the sump. Pumps 90 areinstalled within each casing to remove any water which finds its wayinto the vessel, or to pump the storage area of the stored fluid, ifdesired. Note in 'FIGURE 10 how the lower surface 91 of the vessel issloped toward the pumping sumps.

One of the serious problems encountered in sealed vessels of the typedescribed, is the removal of these pumps for inspection and repair. Themanner of overcoming this diffieulty is shown best by the structuretaught in FIG. 10.

As seen, the casing 64 extends from a surface turbine 93 to near thebottom of sump 85. The pump line shaft 94 connects the lower rotatingelements 90 and turbine 93 for furnishing movement to said lowerelements. Surrounding the line shaft is an intermediate casing 96defining an annulus 97 with the shaft 94. The annulus 97 provides apumping column.

An annulus 98, formed between the casing 64 and the casing 96, isconnected with a gate valve 99 which controls a water supply 100.

When it is desired to remove the pumping elements 90 from the vessel,the pump discharge valve 101 is closed, and the valve 99 is opened.Source 100 provides, through valve 99, a column of water to the annulus98. When the column of water in 98 reaches a sufiicient height tocounteract the LPG pressure within the vessel, valve 99 may be closedand the pump may be pulled. The column of water within casing 64 eifectsa seal to prevent the escape of the stored gas.

After repair and inspection, the pump is lowered into its regularposition, valve 99 is closed and valve 101 is opened and the excesswater in the column is pumped out in the normal manner.

The necessary height for the column of water can be determined fromknown factors, and will be apparent to those skilled in the art.

Thus it will be seen that an improved underground presure vessel storagesystem is constructed which may be adapted for the storage of manyproducts. Improved methods of construction are used which renderordinarily unsuitable locations satisfactory for the storage of a wide"ariety of substances. In addition, an early determination ofsuitability or unsuitability of a site may be made by a pretestingprocedure which simulates with a high degree of authenticity actualoperational conditions of storage prior to extensive and costly miningopera tions.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood, that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described andillustrated.

We claim:

1. In a method of sealing a liner to a surrounding horizontal strata atan intermediate level in a vertical access shaft for an undergroundpressure reservoir, the steps of joining a plurality of utility conduitsto the exterior periphery of a liner in a lengthwise direction prior tointroducing the liner into the shaft, positioning said liner verticallyin the shaft, grouting the space between the liner and shaft,maintaining the interior of said conduits clear during emplacement ofthe liner in the shaft, removing a portion of said liner and saidconduits at the level where the seal is to be made, removing thegrouting and loose earth materials at said level, closing the opening inthe liner, closing said conduits below the level of the seal, andintroducing sealing material to said level from the surface through oneof said conduits.

2. In the method defined in claim 1 the additional step of continuingthe introduction of sealing material through one conduit until saidmaterial fills the space around the liner and is returned to the surfacethrough another of said conduits.

References Cited by the Examiner UNITED STATES PATENTS 285,909 10/83Marsden 166242 411,886 10/89 Clark 166-242 1,049,221 12/12 Frankignoul6150 1,189,516 7/16 Whitney 166-46 1,356,646 10/20 Maher 61-53.'741,993,103 3/35 Labarre 73-84 2,187,871 1/40 Voorhees. 2,302,136 11/42Minton 61'.5 2,659,209 11/53 Phelps 61-.5 2,667,037 1/54 Thomas et al.6l-45 2,678,540 5/54 Lorenz 61-81 2,682,152 6/54 Bierer 6145 2,780,2892/ 57 Garrison. 2,850,937 9/58 Ralston 6145 2,883,833 4/59 Miles 61-.52,928,249 3/60 Miles 61.5 2,957,341 10/60' Menard I 7384 2,971,344 2/61Meade 6l-.5 X 3,004,600 10/61 Henderson et al. 16621 FOREIGN PATENTS720,986 12/54 Great Britain.

EARL J. WITMER, Primary Examiner.

JACOB L. NACKENOFF, JACOB SHAPIRO,

Examiners.

1. IN A METHOD OF SEALING A LINER TO A SURROUNDING HORIZONTAL STRATA ATAN INTERMEDIATE LEVEL IN A VERTICAL ACCESS SHAFT FOR AN UNDERGROUNDPRESSURE RESERVIOR, THE STEPS OF JOINING A PLURALITY OF UTILITY CONDUITSTO THE EXTERIOR PERIPHERY OF A LINER IN A LENGTHWISE DIRECTION PRIOR TOINTRODUCING THE LINER INTO THE SHAFT, POSITIONING SAID LINER VERTICALLYIN THE SHAFT, GROUTING THE SPACE BETWEEN THE LINER AND SHAFT,MAINTAINING THE INTERIOR OF SAID CONDUITS CLEAR DURING EMPLACEMENT OFTHE LINER IN THE SHAFT, REMOVING A PORTION OF SAID LINER AND SAIDCONDUITS AT THE LEVEL WHERE THE SEAL IS TO BE MADE, REMOVING THEGROUTING AND LOOSE EARTH MATERIALS AT SAID LEVEL, CLOSING THE OPENING INTHE LINER, CLOSING SAID CONDUITS BELOW THE LEVEL OF THE SEAL, ANDINTRODUCING SEALING MATERIAL TO SAID LEVEL FROM THE SURFACE THROUGH ONEOF SAID CONDUITS.